For me, the biggest turn on for me in a girl is knowing how to think. Let me clarify: I mean, taking the time to consider things she's heard, then makes a intelligent, logical opinion. I've seen several girls at school who overreact to so many damn things so damn quickly that I find it unbearable(my mother does this too, and I hate it). If a girl can keep her cool, and not jump to any impulsive, ignorant conclusions, then she's automatically a #1 in my book. Intelligence is very important to me. Its makes all the better when a smart girl chooses you instead of a cover model with nothing to his name but looks and money, and you can spend the whole night with her having an intelligent conversation.
Aside from that, I'm going to go against what many men here have said, and say that a girl my height is more for me. I'm a little over 6-feet, but still, I don't like looking down all that much on someone. Also, tall girls normally have long, sexy legs
I agree with the guy who said big eyes. I too, love big eyes. I also like long hair. Short hair is fine, but it has to look good on her.
Size wise, I guess a girl whose at least a bit cautious about their health and weight, as I am trying to be more like. One who may have a bit of chub, but nothing that goes towards unhealthy. Also, skinny anorexics kinda scare me. However, if they're healthy through things like martial arts, then she's immediately got my attention.
Personality wise, a sense of humor is of course important, but a wide, appreciative sense is best. If she's not a big fan of games, film, animation, manga and whatnot, I really don't mind as long they tolerate my appreciation without hostility. If she doesn't cook, that's fine, I like to cook, and I predict that I might be the cook of the relationship. Of course she'd be easy-going and doesn't take too many things too seriously. Again, takes the time to think about what's important.
As you can see, I've had a lot of time to think about this.